Patent application title: IMAGE FORMING APPARATUS

Abstract:

The inclination in the sliding direction to an inner rail of the sheet
cassette is limited by a swing lever which is provided at a roller
bearing support member so as to be protruded through the side of the
upper guide surface of the inner rail when the sheet cassette is moved
and the limitation of the inclination of the sheet cassette by the swing
lever is released when the sheet cassette is pulled out.

Claims:

1. An image forming apparatus having a sheet cassette which is drawably
mounted onto a cassette housing portion comprising:a rail member provided
on the inner wall surface of the cassette housing portion;an engaging
portion which is formed on the wall surface of the side in a direction
perpendicular to the pull out direction of the sheet cassette and engages
with the rail member so that the sheet cassette is moved along the rail
member while the movement in a sliding direction is regulated by the rail
member; anda limitation member which is provided at the engaging portion
of the sheet cassette so as to be able to abut against the rail member in
the sliding direction and limits the inclination in the sliding direction
to the rail member of the sheet cassette when the sheet cassette is moved
along the rail member;wherein the limitation of the inclination of the
sheet cassette by the limitation member is released when the sheet
cassette is pulled out.

2. The image forming apparatus according to claim 1, wherein the
limitation member is located at the downstream in the pull out direction
that is lower than the position of the rail member when the sheet
cassette is pulled out.

3. The image forming apparatus according to claim 1 comprising:a stop
portion which is formed in the downstream end of the rail in the pull out
direction; anda pull-out stop portion which is formed in the downstream
end of the engaging portion of the sheet cassette in the pull out
direction and abuts against the stop portion provided at the rail member
to allow the sheet cassette to be stopped when the sheet cassette is
pulled out;wherein the limitation member is located at the downstream in
the pull out direction that is lower than the position of the rail member
when the pull-out stop portion abuts against the stop portion of the rail
member.

4. The image forming apparatus according to claim 1, wherein the
limitation member is provided at the engaging portion of the sheet
cassette so as to freely projects and be retracted, the limitation member
is protruded from the side of the rail member when the sheet cassette is
moved, and the limitation member abuts against the rail member and is
retracted into the inside of the engaging portion when the sheet cassette
is taken out from the cassette housing portion while the sheet cassette
is inclined and when the sheet cassette is mounted onto the cassette
housing portion.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to an image forming apparatus,
particularly the image forming apparatus formed so that a sheet cassette
is drawably mounted onto a cassette housing portion formed in a main body
of the image forming apparatus.

[0003]2. Description of the Related Art

[0004]An example of image forming apparatuses such as conventional
facsimile machines, copying machines, and printers includes an image
forming apparatus which is formed so that the sheet cassette which houses
the sheet is drawably mounted onto the cassette housing portion formed in
the main body of the image forming apparatus. In such an image forming
apparatus, the sheet housed in the sheet cassette is sequentially
conveyed to an image forming portion at the time of image formation and
images are formed on the sheet in the image forming portion.

[0005]The conventional image forming apparatuses have a drawer apparatus
which drawably mounts the sheet cassette. FIG. 6 illustrates the
structure of such a drawer apparatus.

[0006]The drawer apparatus is formed opposite to the inner wall surface of
the cassette housing portion of the main body of the image forming
apparatus (not shown) and has a frame rail 20 which is a guide when a
sheet cassette 2 is pulled out. Further, the drawer apparatus is formed
on the wall surface of both sides of the sheet cassette 2 opposite to the
frame rail 20 and has a cassette rail 3 which is a guide when the sheet
cassette 2 is pulled out.

[0007]The frame rail 20 includes an outer rail 7 fixed to the inner wall
surface of the cassette housing portion, an inner rail 8 which is
slidably held by the outer rail 7 and in which a locking member 9 is
formed in a downstream end in a pull out direction illustrated by an
arrow (hereinafter referred to as pull out direction). When the sheet
cassette 2 is moved, the cassette rail 3 which is an engaging portion is
engaged with the inner rail 8 which is a rail member. Then, both rails
are moved along the inner rail 8 while the movement of the sheet cassette
2 in a sliding direction is regulated.

[0008]A roller bearing member 10 which rotates on an axis 10a along the
cassette rail 3 of the sheet cassette 2 is formed in the downstream end
of the inner rail 8 in the pull out direction so as to allow the sheet
cassette 2 to be pulled out smoothly. In order to allow the sheet
cassette 2 to be pulled out smoothly, rotating roller bearing members 4
and 5 are formed on the wall surface of both sides of the sheet cassette
2 along an upper guide surface 8a of the inner rail 8 and a lower guide
surface 8b.

[0009]The roller bearing members 4 and 5 are rotatably held by fixed
shafts 4a and 5a provided at a roller bearing support member 6 which has
a part of the cassette rails 3. A locking claw 11 which is locked by the
locking member 9 of the inner rail 8 when the sheet cassette 2 is pulled
out is formed in the downstream end of the roller bearing support member
6 in the pull out direction.

[0010]In such a drawer apparatus, when the sheet cassette 2 is pulled out,
for example, for housing the sheet, the locking claw 11 which is a drawer
stop portion provided at the roller bearing support member 6 is locked by
the locking member 9 which is a stop portion formed on the lower guide
surface 8b of the inner rail 8 as shown in FIG. 7. Further, when the
sheet cassette 2 is pulled out, the sheet cassette 2 slides integrally
with the inner rail 8 along the outer rail 7 under the condition that the
locking claw 11 is locked by the locking member 9.

[0011]Thus, the sheet cassette 2 is pulled out while the inner rail 8 is
integrally pulled out. Thereafter, a stopper (not shown) which is
provided at the inner rail 8 is locked by the outer rail 7, which allows
the sheet cassette 2 to be stopped in the condition that the inner rail 8
is pulled out. The sheet can be housed in the sheet cassette without
separating from the main body of the image forming apparatus by pulling
out the sheet cassette 2 in such a manner.

[0012]When the sheet cassette 2 is detached from the main body of the
image forming apparatus, the downstream of the sheet cassette 2 in the
pull out direction is lifted upward in the condition that the sheet
cassette 2 is pulled out from the main body of the image forming
apparatus as shown in FIG. 8. Thus, the engagement of the locking claw 11
of the sheet cassette 2 and the locking member 9 of the inner rail 8 is
separated. The sheet cassette 2 can be detached (drawn out) from the main
body of the image forming apparatus by pulling out the sheet cassette 2
under the condition.

[0013]Here, an abutting portion 11a against the locking member 9 of the
locking claw 11 of the roller bearing support member 6 (shown in FIG. 8)
and an abutting portion 9a against the locking claw 11 of the locking
member 9 of the inner rail 8 are inclined so as to guide the movement in
a take out direction of the sheet cassette 2, namely, the movement
obliquely upward. Thus, in taking out the sheet cassette 2, when the
downstream of the sheet cassette 2 in the pull out direction is lifted,
the sheet cassette 2 is lifted obliquely upward while being guided by the
inclination of the abutting portion 11a of the locking claw 11 and the
abutting portion 9a of the locking member 9.

[0014]Further, a concave portion 6a is formed on the upper surface of the
roller bearing support member 6 (cassette rail 3) so that the roller
bearing support member 6 (cassette rail 3) does not abut against the
inner rail 8 when the sheet cassette 2 is lifted in such a manner.

[0015]For example, in the case where the image forming apparatus is placed
in a low position, when a user tries to pull out the sheet cassette 2,
the user needs to grip a handle of the sheet cassette 2 to pull out the
sheet cassette 2 as it is tilted. Here, in the case of such a structure
of the drawer apparatus, when the user tries to pull out the sheet
cassette 2 as it is tilted, the locking claw 11 of the sheet cassette 2
does not abut against the locking member 9 of the inner rail 8 as shown
in FIG. 8 and the sheet cassette 2 is drawn out.

[0016]An example of the structure for solving such problems includes a
structure having a stop member which allows the sheet cassette 2 to be
stopped at a predetermined drawing position without drawing out when the
sheet cassette 2 is pulled out. The technique is disclosed in Japanese
Patent No. 3571910.

[0017]However, in the case of conventional image forming apparatuses
having such a stop member, when the user draws out the sheet cassette,
the stop member has to be moved from the position where the sheet
cassette is stopped at the drawing position to the position where the
sheet cassette can be drawn out.

[0018]When the drawn out sheet cassette is mounted, the stop member has to
be moved from the position where the sheet cassette can be drawn out to
the position where the sheet cassette is stopped at the drawing position.
Therefore, when the sheet cassette is drawn out or mounted, the operation
is complicated.

SUMMARY OF THE INVENTION

[0019]The present invention has been achieved in view of the above
circumstances and there is provided an image forming apparatus in which
the sheet cassette can be reliably pull out and the sheet cassette can be
easily drawn out and mounted.

[0020]According to the present invention, there is provided an image
forming apparatus having a sheet cassette which is drawably mounted onto
a cassette housing portion which includes a rail member provided on the
inner wall surface of the cassette housing portion, an engaging portion
which is formed on the wall surface of the side in a direction
perpendicular to the pull out direction of the sheet cassette and engages
with the rail member so that the sheet cassette is moved along the rail
member while the movement in a sliding direction is regulated by the rail
member, and a limitation member which is provided at the engaging portion
of the sheet cassette so as to be able to abut against the rail member in
the sliding direction and limits the inclination in the sliding direction
to the rail member of the sheet cassette when the sheet cassette is moved
along the rail member, where the limitation of the inclination of the
sheet cassette by the limitation member is released when the sheet
cassette is pulled out.

[0021]Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a perspective view of the image forming apparatus
according to the embodiment of the present invention.

[0023]FIG. 2 is a perspective view illustrating the structure of the
drawer apparatus formed in the image forming apparatus.

[0024]FIG. 3 is a side view illustrating the condition that the sheet
cassette of the drawer apparatus is housed.

[0025]FIG. 4 is a view illustrating the condition that the sheet cassette
of the drawer apparatus is pulled out from the main body of the
apparatus.

[0026]FIGS. 5A and 5B are views illustrating the condition that the sheet
cassette of the drawer apparatus is taken out from the main body of the
apparatus.

[0027]FIG. 6 is a view illustrating the structure of a conventional drawer
apparatus formed in the image forming apparatus.

[0028]FIG. 7 is a view illustrating the condition that the sheet cassette
of the conventional drawer apparatus is pulled out from the main body of
the apparatus.

[0029]FIG. 8 is a view illustrating the condition that the sheet cassette
of the conventional drawer apparatus is taken out from the main body of
the apparatus.

DESCRIPTION OF THE EMBODIMENTS

[0030]Hereinafter, an exemplary embodiment of the present invention will
be specifically described with reference to the drawings.

[0031]FIG. 1 is a perspective view of the image forming apparatus
according to the embodiment of the present invention. An image forming
apparatus 100 and a main body of the image forming apparatus 101
(hereinafter referred to as the main body of the apparatus) are shown in
FIG. 1. The image forming portion (not shown) and a sheet feeding
apparatus (not shown) which feeds the sheet housed in the sheet cassette
2 which is drawably mounted in the main body of the apparatus 101 to the
image forming portion are provided in the main body of the apparatus 101.

[0032]In FIG. 1, a cassette housing portion is formed on the lower side of
the main body of the apparatus 101. As shown in FIG. 1, when the sheet is
housed or supplied, the sheet cassette 2 housed in the cassette housing
portion 102 is pull out toward the front side of the main body of the
apparatus 101.

[0033]The frame rail 20 which includes the outer rail 7 fixed to the inner
wall surface 102a and the inner rail 8 slidably held at the outer rail 7
and guides the drawing and mounting of the sheet cassette 2 is provided
at the inner wall surface 102a of the cassette housing portion 102. In
this regard, the frame rail 20 is formed on the other inner wall surface
(not shown) opposed to one side of the inner wall surface 102a of the
cassette housing portion 102.

[0034]The cassette rail 3 which is provided opposite to the frame rail 20
and serves as a guide when the sheet cassette 2 is pulled out is formed
on the wall surface of both sides in a direction perpendicular to the
pull out direction of the sheet cassette 2.

[0035]The drawer apparatus drawably mounts the sheet cassette 2 in the
main body of the apparatus 101 with the frame rail 20 provided at the
inner wall surface 102a of the cassette housing portion 102 and the
cassette rail 3 provided at the sheet cassette 2.

[0036]When the sheet is housed in the sheet cassette 2 by the drawer
apparatus, the sheet cassette 2 can be pulled out to the position where
the sheet can be housed. In the drawer apparatus, when the sheet cassette
2 is drawn out, the downstream (front) in the pull out direction of the
sheet cassette 2 is pulled upward after pulling out the sheet cassette 2
and then drawn out obliquely upward.

[0037]FIG. 2 is a perspective view illustrating such a structure of the
drawer apparatus. FIG. 3 is a side view illustrating the condition that
the sheet cassette 2 of the drawer apparatus is housed. The same symbols
as those used in FIG. 7 are assigned to the same portions as or
equivalent portions to those shown in FIGS. 2 and 3.

[0038]In FIGS. 2 and 3, a swing lever 12 is a limitation member which
limits the inclination in the sliding direction to the inner rail 8 of
the sheet cassette 2 when the sheet cassette 2 is moved. The swing lever
12 is held the roller bearing support member 6 provided at the sheet
cassette 2 so as to be able to swing on an axis 12a.

[0039]An abutting portion 13 in which the top end is protruded from the
concave portion 6a which is provided so that the upper surface of the
roller bearing support member 6 is dented to the side of the upper guide
surface of the inner rail 8 and which can abut the upper guide surface 8a
of the inner top of the inner rail 8 is provided at the swing lever 12.
Further, an elastic portion 14 which applies a force to the direction
that the abutting portion 13 is protruded from the roller bearing support
member 6 is integrally formed at the swing lever 12. In this regard,
elastic members such as coil springs may be connected for use without
integrally forming the elastic portion.

[0040]The swing lever 12 is welded to an abutting wall (not shown) which
is provided at the roller bearing support member 6 by elasticity of the
elastic portion 14. Usually, the swing lever 12 is elastically held at
the first position in the condition that the abutting portion 13 is
protruded from the upper surface of the roller bearing support member 6.
In the condition that the sheet cassette 2 is mounted in the cassette
housing portion 102, the swing lever 12 is in the first position. For
that reason, even if an upward lifting force is applied to the sheet
cassette 2, the abutting portion 13 of the swing lever 12 abuts against
the upper guide surface 8a of the inner rail 8. Accordingly, the movement
upward (inclination) of the sheet cassette 2 is limited.

[0041]That is, the flat surface of the upper portion of the abutting
portion 13 of the swing lever 12 is located at the upper portion of the
axis 12a and formed parallel to the upper guide surface 8a. Thus, even if
the flat surface of the upper portion of the abutting portion 13 abuts
against the upper guide surface 8a, the swing lever 12 cannot be swung.
For that reason, the swing lever 12 abuts against the upper guide surface
8a and an upward inclination of the upper portion of the sheet cassette 2
is limited.

[0042]The swing lever 12 in the condition that the abutting portion 13 is
protruded from the roller bearing support member 6 is provided at the
sheet cassette 2 in such a manner. Therefore, in pulling out the sheet
cassette 2, the movement upward (inclination) of the sheet cassette 2 is
limited even if the upward lifting force is applied to the sheet cassette
2.

[0043]When the user tries to take out the sheet cassette 2 as it is tilted
after pulling out the sheet cassette 2 to the drawing position as
described below, the swing lever 12 is swung against an elastic force of
the elastic portion 14 and moved to the second position where the
abutting portion 13 is retracted from the upper surface of the roller
bearing support member 6. Thus, even if the swing lever 12 is provided,
the sheet cassette 2 can be detached (drawn out).

[0044]Subsequently, such an operation of the swing lever 12 when the sheet
cassette 2 is pulled out will be described.

[0045]In order to pull out the sheet cassette 2, when the sheet cassette 2
is moved in a direction pulled out from the main body of the apparatus
101, namely, in the direction of an arrow in FIG. 3, the swing lever 12
is held at the first position by the elastic portion 14.

[0046]Thus, even when the upward lifting force is applied to the sheet
cassette 2 in the middle of pulling out the sheet cassette 2, the
abutting portion 13 of the swing lever 12 abuts against the upper guide
surface 8a of the inner rail 8. Consequently, the movement upward of the
sheet cassette 2 is limited. Thus, even when the upward lifting force is
applied to the sheet cassette 2 in the middle of pulling out the sheet
cassette 2, the sheet cassette 2 moves along the inner rail 8 without
inclining in the sliding direction and lifting the downstream in the pull
out direction.

[0047]In this regard, FIG. 4 is a view illustrating the condition of the
drawer apparatus when the sheet cassette 2 is pulled out from the main
body of the apparatus 101. As shown in FIG. 4, when the sheet cassette 2
is pulled out from the main body of the apparatus 101 the locking claw 11
of the roller bearing support member 6 is locked by the locking member 9
of the inner rail 8. Thus, the sheet cassette 2 can be stopped at the
predetermined drawing position.

[0048]At this time, the swing lever 12 is located at the downstream in the
pull out direction that is lower than the downstream end of the inner
rail 8 in the pull out direction. The swing lever 12 and the inner rail 8
are set so that contact between the abutting portion 13 of the swing
lever 12 and the upper guide surface 8a of the inner rail 8 can be
ensured until when the sheet cassette 2 is pulled out. Thus, the sheet
cassette 2 will not be inclined and will not be drawn out from the main
body of the apparatus 101 despite the user's intent until the sheet
cassette 2 is pulled out from the main body of the apparatus 101.

[0049]Subsequently, effects of the swing lever 12 when the user draws out
the sheet cassette 2 from the main body of the apparatus 101 will be
described.

[0050]In the case where the sheet cassette 2 is detached from the main
body of the apparatus 101, the sheet cassette 2 is lifted. Thus, the
sheet cassette 2 is moved in the direction of an arrow A by the
inclination of each of the abutting portions 9a and 11a of the locking
member 9 of the inner rail 8 and the locking claw 11 of the roller
bearing support member 6 as shown in FIG. 5A. Then, the engagement of the
locking claw 11 of the roller bearing support member 6 and the locking
member 9 of the inner rail 8 is separated.

[0051]In this case, the abutting portion 13 of the swing lever 12 which is
protruded from the concave portion 6a formed on the upper surface of the
roller bearing support member 6 abuts against a downstream end 15 of the
inner rail 8 in the pull out direction as shown in FIG. 5B.

[0052]Since the side surface of the abutting portion 13 abuts against the
side end 15 of the inner rail 8, the swing lever 12 is swung against the
elastic force of the elastic portion 14 in a counterclockwise direction
and then moved to the second position where the abutting portion 13 is
retracted from the upper surface of the roller bearing support member 6.
As a result, the sheet cassette 2 can be taken out obliquely upward
(drawn out) from the main body of the apparatus 101 without being
interfered by the swing lever 12.

[0053]In the case where the sheet cassette 2 is mounted, the sheet
cassette 2 is inserted into the side of the main body of the apparatus
while the sheet cassette 2 is inclined and the cassette rail 3 of the
sheet cassette 2 is engaged with the inner rail 8. At this time, the
abutting portion 13 abuts against the inner rail 8, the swing lever 12 is
swung against the elastic force of the elastic portion 14 in the
counterclockwise direction and thus the abutting portion 13 is retracted
from the upper surface of the roller bearing support member 6. As a
result, the sheet cassette 2 can be inserted into the main body of the
apparatus 101 without being interfered by the swing lever 12.

[0054]Thus, the sheet cassette 2 can be reliably pulled out by limiting
the inclination of the sheet cassette 2 when the sheet cassette 2 is
moved and releasing the control of the inclination of the sheet cassette
2 when the sheet cassette 2 is pulled out. Further, the sheet cassette 2
can be easily drawn out and mounted.

[0055]In this regard, the case where the abutting portion 13 of the swing
lever 12 is protruded from the upper surface of the roller bearing
support member 6 has been described. However, the present invention is
not limited thereto. The same effect can be obtained, for example, when a
swing lever having an abutting portion which is protruded downward from
the roller bearing support member 6 is provided at the roller bearing
support member 6 so as to freely projects and be retracted and the
abutting portion is protruded through an inner rail side (rail member
side) in moving the sheet cassette 2.

[0056]While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0057]This application claims the benefit of Japanese Patent Application
No. 2007-226362, filed Aug. 31, 2007, which is hereby incorporated by
reference herein in its entirety.